1. Field of the Invention
The present invention relates to a chuck device having a pair of grippers that are angularly movable under the pressure of a fluid respectively into substantially parallel positions for gripping a workpiece.
2. Description of the Related Art
Heretofore, chuck devices have been used to grip workpieces. FIG. 5 of the accompanying drawings shows a conventional chuck device 1. As shown in FIG. 5, the conventional chuck device 1 comprises a body 2 having a cylinder chamber 3 defined therein and a. piston mechanism 5 having a piston 4 reciprocally movable axially in the cylinder chamber 3. The piston mechanism 5 also has a piston rod 6 with an outer end thereof projecting out of the body 2, and a plate 7 is fixed to the outer end of the piston rod 6. A pair of grippers 10a, 10b is connected to respective opposite ends of the plate 7 by respective joint plates 9a, 9b that are pivotally supported on the plate 7 by pins 8a, 8b. The grippers 10a, 10b are angularly movably supported in a recess 12 defined in the body 2 by respective pins 11a, 11b.
When the grippers 10a, 10b are angularly moved 90.degree. toward each other, as indicated by the solid lines, about the pins 11a, 11b by the piston rod 6 which is retracted into the body 2. the grippers 10a, 10b grip a workpiece (not shown). When the grippers 10a, 10b are angularly moved 90.degree. away from each other, as indicated by the two-dot-and-dash lines, about the pins 11a, 11b by the piston rod 6 which projects out of the body 2, the grippers 10a, 10b releases the workpiece.
With the conventional chuck device 1, linear movement of the piston rod 6 is converted into angular movement of the grippers 10a, 10b by the joint plates 9a, 9b.
The pins 8a, 8b and the pins 11a, 11b are spaced from each other by respective interaxial distances A.sub.1, A.sub.2. These interaxial distances A.sub.1, A.sub.2 may be different from each other due to dimensional errors. If the interaxial distances A.sub.1, A.sub.2 are different from each other, then the grippers 10a, 10b may not extend parallel to each other when they are angularly moved toward each other. Accordingly, the grippers 10a, 10b may fail to provide a required level of accuracy about parallelism therebetween when angularly moved toward each other.
Dust or dirt particles that find their way into the opening 12 tend to be attached to the pins 8a, 8b, 11a, 11b and unduly wear them to the point where the grippers 10a, 10b cannot smoothly be angularly moved about these pins.
When the grippers 10a, 10b are angularly moved a certain angle, gaps 13 are created between the body 2 and the grippers 10a, 10b, allowing dust or dirt particles to enter the opening 12.